Field of the Invention
The invention concerns a device for cleaning a driven cylinder of a printing press by means of a wash cloth which is unwound gradually by a magazine roller, is moistened with a cleaning fluid, is conducted over a pressure mechanism pressed against the cylinder to be cleaned and is wound up on a take up roller.
The cylinders of the printing presses and especially their rubber cylinders get dirty during the operation of the printing press after a certain time and must then be cleaned. When compared with known cleaning mechanisms which work with rotating brushes, wetted with a washing liquid, which lie against the cylinder to be cleaned, U.S. Pat. No. 2,525,982 has brought about some progress because, in accordance with the characteristics named at the outset, a wash cloth, gradually wetted with a cleaning fluid is applied to the surface to be cleaned of the concerned cylinder. In the case of the named U.S. patent, however, it is disadvantageous that the pressure mechanism is designed as a pad, which by means of a control mechanism applies the wash cloth to the surface of the cylinder to be cleaned. In cross-section, the pad is T-profiled, so that the cleaning fluid can be fed onto an attachment facing away from the surface to be cleaned. With this arrangement, no precise time-oriented control of the wetting of the wash cloth is possible, because the washing fluid must constantly traverse the distance from the wick-like pad to the rear side of the wash cloth. A certain amount of washing fluid is contantly being collected in this wick-like pad, which goes to the wash cloth and from there is applied to the surface of the cylinder to be cleaned. Thus, it is also not possible to rub the cylinder to be cleaned dry, i.e., with a dry wash cloth part it is not possible to carry out the described relative movement between the cylinder and the wash cloth. Finally, it is disadvantageous because the pressure pad is not moved along with the gradual forward movement of the wash cloth; therefore, additional forces are exerted on the wash cloth. On the other hand, the wash cloth must be porous in order to be able to absorb sufficient washing fluid.
Moreover, it is disadvantageous in the case of the above-named mechanism that the drive for gradual transport of the wash cloth onto the take-up roller is provided in such a manner that it is transported at each step through the same angle of rotation. With the changing diameter of the wash cloth on the take-up roller, a different length of wash cloth is conducted past the pressure pad and, thus, is used for the cleaning operation. The rotating step for the drive of the take-up roller must be so designed that at the start of the take-up operation, when there is only a small amount of wash cloth on the take-up roller, a sufficient length of wash cloth is transported by this rotating step. The result of this is, however, that ever increasing amounts of wash cloth are used up with each subsequent rotation step, and an unnecessarily large amount of wash cloth is used up.